SOLAR EXTREME EVENTS AND GRATE

GEOMAGNETIC STORMS 

E.E. Antonova, M.V. Stepanova 

Skobeltsyn Institute of Nuclear Physics Moscow State University, Moscow, 119992, Russia; tel. +7-095-9392488; fax:

+7-095-9390896, e-mail: antonova@orearm.msk.ru

•Iyemori and Rao [1996] problem (decay of the Dst field of geomagnetic disturbance after substorm onset)•The topology of high latitude magnetosphere•Formation of plasma pressure profile during magnetic storm •Upper limit of the increase of the inner magnetospheric plasma pressure •Comparison of theory predictions with the results of experimental observations

si12_2000_197_mapped.mpeg

Difficulties of the concept of contribution of TC in Dst:1. Problem of pressure balance on the magnetopauseIn the condition of magnetostatic equilibrium plasma pressure is constant on the current line as p][jB

Plasma pressure on the tail current line can not be larger then dynamic+ static+magnetic.

pressure in the magnetosheath.

02 2/ lobetail Bp Limitation on the contribution of TC in Dst

•CRC is concentrated in the region of quasitrapping.•CRC is mapped on the most part of the auroral oval. •Current lines in CRC are closed inside the magnetosphere.•CRC is a high latitude continuation of ordinary ring current (RC).•It is necessary to introduce energy content of CRC in DPC relation.

transport from the tail

transport from the ionosphere

avalanche-like behavior

Sketch illustrated the mechanisms of the storm-time redistribution of plasma pressure

The upper limit of the inner magnetospheric particle feeling is determined by the stability of the distribution of the plasma pressure. This limit exists in spite of the action of different acceleration and transport mechanisms of plasma particles.

Kadomtsev’s [1963] criterion of the stability of the azimuthally symmetric distribution of isotropic plasma pressure in the magnetic trap in the region of low has the form:

p<pcrit, where p=p(W), W=dl/B is the flux tube volume, pcritW

=const,

=const equal to 7/4 for the case of the dipole magnetic field. Plasma tongues begin to form if p>pcrit and the magnetic trap

loses part of plasma population.

Plasma pressure inside the magnetosphere can be increased infinitely or definite limitations exist?

The existence of maximal possible plasma pressure profile and sharp equatorial RC boundary give the possibility to obtain the dependence of Dst on the

position of plasma pressure maximumDessler and Parker [1959]; Sckopke [1966] relation has the form

DeqT BB 3/2/

022 3/4 EED RB nT102.3 4eqB

ER

prdrdz 3 p(L)=pex(Lex/L)7

4473

2 ininexexE LconstLLpRA

Lin is the position of the internal boundary of the ring current.

02 2/ lobeex Bp

Tverskoy [1997] relation ex

in

W

WE

critst dW

L

W

dW

dWp

RD

4

3 0*

Win and Wex are the values of flux tube volume at the inward

and outward boundaries of the ring current 4

04 35/32 LWBLRW eqE in the dipole magnetic field

In case of a quasidipole magnetic field accuracy of the Tverskoy [1997] relation reaches 20% when the equatorial magnetic field differs from the dipole one in less than 100%

If p(L)=pex(Lex/L)7 and 02 2/ lobeex Bp

nTl 140

27

70

27 472

470* inex

eq

lobeinexex

eq

critst LL

B

BLLp

BD

nTl 1075.2 44

max

inst LD

If Lex =10, Blobe=21,4 nTl

nTl 1075.2 4max

4

max

LDstDependence

where Lmax determines also the position of the peak intensity of

fluxes of relativistic electrons, which appear during storm recovery phase, was obtained experimentally by Tverskaya [1986], Tverskaya et al. [2003].

L-position of auroral electrojet latitude coincides with the L-position of the plasma pressure maximum and L-position of the peak intensity of fluxes of relativistic electrons during grate magnetic storm.

Tverskaya et al. [2003]

Analysis of the maximal possible plasma pressure profile inside the magnetosphere gives possibility to obtain the natural explanation of Dst dependence on L-position of the plasma pressure maximum

Geomagnetic storm March 1-8Geomagnetic storm March 1-8

March 01, 1982 passage, the storm main phase

IGRF model is used. Fitting by the

dependences pL-s s=7.81.1.

Theory prediction s=7

CONCLUSIONS•The contribution of tail current in Dst value is limited by the condition of the magnetopause pressure balance.•It is possible to restore the traditional interpretation of Dst as the measure of particle energy inside the magnetosphere and the applicability of DPS relation taking into account the existence of CRC - the high latitude continuation of the ring current•The analysis of the formation of the convectively equilibrated distribution of the radial plasma pressure gives the possibility to explain the dependence of maximum of Dst-variation on the position of plasma pressure maxima, which is near to the position of auroral electrojets.•Plasma pressure radial profile obtained on the basis of low orbiting Aureol satellite confirm the theory prediction on the formation of plasma pressure distribution during storm time main phase corresponding to pL-7.